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2G AC fan will not come on with DSMLink "Turn Fans To Full" button

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406_Talon

Supporting Member
116
13
Jun 30, 2014
Kalispell, Montana
So I swapped my crappy mishimoto fans out for a nice Derale pusher and a FAL puller. I put the puller on the radiator fan side and the pusher on the AC side, due to packaging constraints.

Both fans are 2 wire, so the OEM 4 wire high and lo wires on harness side are tied together on both sides. I have a jumper wire between post 4 of the rad fan lo and the AC fan lo relays to trigger them both together per several threads on here. My mishimoto fans both came on this way when I clicked the AC button on and turned the blower on. They also both came on when I used DSMLink's "turn both fans on full" setting.

After connecting everything, I tested it with link, and both fans came on. The AC button worked too. I buttoned up the bumper and went to drive it to test, and I figured I'd give it one last check, hit the switch in DSMlink and only the passenger side radiator fan comes on. Nothing happens with the AC switch. The AC fan won't come on no matter what I do.

I tested it with a separate battery and it works fine. I tested the old Mishimoto fan in that spot and it no longer works either, but also tests fine on a battery. I have swapped the relays all around to test them and they all yield the same results.

Am I missing a fuse or anything? I'm gonna try to test for voltage at the connectors tomorrow. My pusher AC fan draws 24 amps when it's on, I figured the OEM relays and wires could handle that with the wires doubled up. Was I wrong?

What I was considering is just running a new relay and wire with inline fuse, and tying the ground to the OEM relay with a switch in line so I would still have OEM style control, and I'd also have a switch for between autocross runs to cool off in line. Should this plan work ok?

Am I missing any components, ie; fuses or relays other than the 4 hi/lo relays? Should the OEM wires be able to handle running a 24 amp fan? Is it likely that I burned a wire?

Any suggestions would be much appreciated I hate having to let my baby sit over a damn fan.
 
It's Multimeter and wiring diagram time.

DSMLink's control starts as the ECU pins. The are active low, meaning the ECU pulls the pin to ground to make the relay activate. When the ECU isn't trying to make the fan run the output floats at the voltage the relay coil is at.

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I can't find the rest of the circuit ATM so start with making sure that you have battery voltage to these pins with the ignition in engine off and that once you tell DSMLink to turn the fans on these pins go to 0v.

If you don't have battery voltage to start with you need to look at the relays and make sure they get power and work. If the ECU pins don't go low your wiring may have caused the ECU driver to fail. The ECU needs the resitive load of the relay coil to protect the transistor from trying to drain the battery through it.
 
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